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POSIX: use mincore to detect impending doom 

Call to mmap (or next malloc) will likely fail if there are already
mapped pages within the region we want to map ourselves. Using mincore
we can detect if such pages exist and warn user about what's going to
happen.
This commit is contained in:
Michał Janiszewski 2015-12-08 23:53:43 +01:00
parent 08fc36ee49
commit 3d0fcc948d
1 changed files with 38 additions and 1 deletions
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39
src/openrct2.c
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@ -513,6 +513,43 @@ static bool openrct2_setup_rct2_segment()
off_t file_size = 6750208;
int len = 0x01429000 - 0x8a4000; // 0xB85000, 12079104 bytes or around 11.5MB
int pageSize = getpagesize();
int numPages = (len + pageSize - 1) / pageSize;
unsigned char *dummy = malloc(numPages);
int err = mincore((void *)0x8a4000, len, dummy);
bool pagesDirty = false;
if (err != 0)
{
err = errno;
#ifdef __linux__
// On Linux ENOMEM means all requested range is unmapped
if (err != ENOMEM)
{
pagesDirty = true;
perror("mincore");
}
#else
pagesDirty = true;
perror("mincore");
#endif // __linux__
} else {
log_warning("mincore ok");
for (int i = 0; i < numPages; i++)
{
if (dummy[i] != 0)
{
pagesDirty = true;
void *start = (void *)0x8a4000 + i * pageSize;
void *end = (void *)0x8a4000 + (i + 1) * pageSize - 1;
log_warning("page %p - %p has flags: %x, you're in for bad time!", start, end, dummy[i]);
}
}
}
free(dummy);
if (pagesDirty)
{
log_error("Found already mapped pages in region we want to claim. This means something accessed memory before we got to and following mmap (or next malloc) call will likely fail.");
}
// section: rw data
gDataSegment = mmap((void *)0x8a4000, len, PROT_READ | PROT_WRITE, MAP_FIXED | MAP_ANONYMOUS | MAP_SHARED, 0, 0);
if (gDataSegment != (void *)0x8a4000) {
@ -530,7 +567,7 @@ static bool openrct2_setup_rct2_segment()
}
void *fbase = mmap(NULL, file_size, PROT_READ, MAP_PRIVATE, gExeFd, 0);
int err = errno;
err = errno;
log_warning("mmapped file to %p", fbase);
if (fbase == MAP_FAILED)
{